Birmingham City supporters have called on the Football League to investigate concerns that Carson Yeung, who remains a substantial shareholder despite his conviction in Hong Kong on £55m money-laundering charges, may continue to wield influence at the club. According to documents filed on the Hong Kong Stock Exchange, Yeung, who when sentenced on Friday could be imprisoned for a maximum seven years, retains just under 20% ownership of the parent company, Birmingham International Holdings.

He resigned as the football club's chairman and as a director of BIHL early last month, after conducting and being the most visible figure during and since BIHL's £81.5m takeover of City in 2009. His resignation places him beyond the league's requirement that owners and directors of its clubs have no convictions for dishonesty, which applies only to shareholders owning 30% or more. The league's rule does, though, also apply to "shadow" directors, "persons exercising 'control'" over a club, and "persons in accordance with whose directions or instructions the club's management are 'accustomed to act'".

In a statement after the news of Yeung's conviction, the League said it was satisfied City's present board and ownership comply with its rules. The League has since confirmed it is not planning to conduct an investigation, although it will look at any evidence brought to it.

Steve McCarthy, chairman of the supporters' Blues Trust, said he had obvious questions over the distance from Yeung there will be for the Birmingham City board, which includes Yeung's son Ryan, Yeung's brother-in-law Shui Cheong Ma, and Panos Pavlakis, reported to be Yeung's future brother-in-law. Peter Pannu, City's acting vice-chairman, who was paid almost £1m in salary and consultancy fees last year for work relating to Birmingham City, is a long-term Hong Kong-based associate of Yeung's.

"We are very disappointed that the Football League is not actively planning to investigate the ownership and running of the club in the light of Carson Yeung's conviction," he said. "We are desperate for these people to go now and hand the club to somebody who will have its best interests at heart, ideally with the involvement of supporters in owning a stake."

Pannu, emphasising that Yeung is not a director of the club or holding company, told the Birmingham Mail from Hong Kong: "I understand the concerns people may have in that Carson Yeung may still run the show from the prison by proxy via his relatives who are on the UK boards. I can only say that this is speculation and conjecture and the interest of the club comes first."

Carson Yeung, serving a six-year prison sentence for money-laundering, was convicted of two other criminal offences in the past decade yet the Premier League still allowed him to take over Birmingham City in 2009

Birmingham City are unhappy with comments made by the referee James Linington during Wednesday night's 3-3 draw against Burnley but the Midlands club have decided against pursuing any formal complaint about the incident